Apparatus for drilling wells of large radii curved bores



May 15, E956 J. A. ZUBLIN 2,745,635

APPARATUS FOR DRILLING WELLS OF LARGE RADII CURVED BORES Filed July 20,1953 4 SheetsS'neet l ATTORNEYS CURVE@ BORES J. A. ZUBLIN May 15, 1956APPARATUS FOR DRILLNG WELLS OF LARGE RADII 4 Sheets-Sheet 2 Filed July20, 1955 X/.S OFDR/LL GUIDE 1N VENTOR Jah/iwi. Z wb .7/1/'12/ATTORNEYS 1. A. ZUBLIN 2,745,635

APPARATUS FOR DRILLING WELLS OF LARGE RADII CURVEQD BORES May 15, 1956Filed July 20, 1953 ATTORNEYS May 15, 1956 J. A. ZUBLIN 2,745,635

APPARATUS FOR DRILLING WELLS oF LARGE RADII CURVE@ BoREs Filed July 20,1953 4 Sheets-Sneet 4 INVENTOR John/A. Zll/l l I I, n. f A H al f A Il..lllwwml N w ATTORNEYS United APPARATUS FOR DRLUNG WELLS F LARGE RABHCURVED BORES This invention relates to a method and apparatus fordrilling oil wells with oriented curved bores of large radii. Morespecifically the invention is directed to a method and apparatus bywhich oriented curved bores of large radii may be effectively drilledwith but one round trip of the drilling equipment.

The need for the drilling of deecting bores having as their purpose therecovery of oil from points in a producing formation horizontally spaceda substantial distance from the point of initiation of the vertical wellbore, has become increasingly pronounced with attempts to recover oil,for example from under-Water formations. Indeed there are many instanceswhere real need for the drilling of a deecting bore in a given azimuthis apparent.

The present invention is not concerned with the production of smallradii curved deviating bores such as draining holes drilled directlyfrom a vertical Well bore laterally into the producing formation, butrather is concerned with the production of a deecting bore as acontinuation of an initially straight well bore in the original drillingof which the bore is deected in a curved path having a radius of theorder ot" LCG() to 2,600 feet or larger.

In prior art practices of drilling deecting bores, the expedient ofusing whipstocks has been largely resorted to. Generally speaking, thetubular drill strings employed in rotary drilling have sufdcientinherent exibility to permit of their deviation from the vertical in anamount approximating about three degrees per hundred feet of length ofdrilling string. Again speaking generallly, whipstocks set in a verticalwell bore for the purpose of causing a deection of the drill bit usuallycontemplate a deflection from the vertical of from around three degreesto tive degrees.

In practice it has been found that when drilling a deecting bore throughthe medium of the whipstock, the drilling string, after it passes thewhipstock, tends to follow the path of least resistance and return to astraight line. The tendency of the drill string to return to itsnormally straight form by reason of its natural semiresientcharacteristics is encouraged by the force of gravity actinU downwardlyon the deviating end of the drill string. Because of this inherenttendency of the rotary drill string to follow the path of leastresistance, it has been the prior art practice in the drilling ofdeecting bores through the use of whpstoclrs to drill a limited distancebeyond the point of setting of a given whipstock; to then withdraw thedrill string and bit from the well bore and set another whipstock at thelower depth to which the deecting bore had been drilled, this procedurebeing repeated throughout the drilling of the dellecting bore. Suchpractice has entailed the necessity for a complete round-trip for thedrilling equipment each time a whipstock is set. Each round-trip andeach setting of the whipstock entails hazards that, quite apart from thesheer loss of time involved, render the drilling of deiecting bores oflarge radii very costly,

tate Mem o F 2,745,635 Patented May 15, 1956 In the drilling of curvedbores, as well as straight bores, through dierent formations, it hasbeen found that such bores will not have a uniform diameter throughouttheir length. A drill bit of a certain size, in the hardest sections ofthe variable formation, will drill a hole substantially equal to the bitdiameter. ln softer sections of the formation, the same bit will drill ahole somewhat larger or oversize in relation to the bit diameter. Thisdifterence in diameter along the length of the bore may vary as much asseveral inches. Accordingly, it becomes necessary that an apparatus todrill curved bores be adaptable to the various diameters produced by thesame size bit in drilling through a formation of varying hardness.

Furthermore, in oil well drilling of curved bores, it often becomesnecessary to change the radius of the curved bore either to correct thedirection of the bore hole, or to change the desired termination pointfor such bore hole. Presently available equipment for performing theseoperations has been found to be ineffective in controlling the directionof drilling, and also requires the withdrawal of the apparatus with asubsequent change of the parts in order to correct the direction orchange the desired terminus of the bore hole.

It is a purpose and object of the present invention to provide a methodand apparatus by which a deflecting bore may be produced throughconventional rotary drilling techniques as a direct continuation of aninitiated straight well bore.

Furthermore, it is the purpose and object of the present invention toprovide a greatly simplified method and apparatus for drilling deectingbores of large radii through the medium of which it is possible tocompletely eiirninate the use of whipstocks and complete the drilhng ofthe dellecting bore or even a series of deilecting bores withoutremoving the apparatus from the well.

More specifically, it is the purpose and object of this invention toprovide a method and apparatus for initiating and continuing thedrilling of a deecting bore at substantially the same fixed radiussuciently large to lie within the limits of inherent exibility of theconventional rotary drill string, the curve of such deilecting boreconforming to such xed radius irrespective of variations in diameter ofthe bore caused by variations in the characteristics of the formationthrough which the bore extends.

From au apparatus standpoint, the purpose and object of this inventionis to provide a unit suspendible from the lower end of a rotary drillstring susceptible of manipulation in such a manner as to eect theinitiation and continued drilling of a curved deflecting bore of a largeradius irrespective of bore diameter variations caused by varyingformation hardness Without the use of other elements orinstrumentalities than those suspended from and carried by andinsertable into a weli here through the medium of a conventional rotarydrill string.

The expression curved bores of large radii as used herein is intended toidentify and define degrees of curvature attainable through the inherentflexibility of a normal rotary drill string. Generally speaking, theradii of delecting bores in the drilling of which the present inventionis addressed lie within the limits of LGO@ to 3,000 feet. it will bereadily recognized, however, that this range of radii is in no waylimiting as to the scope of this invention. As the radius of curvatureof the deecting bore increases toward infinity, such deflecting boreapproaches a more nearly straight well bore. As will be obvious from thedescription hereinafter, certain variations in the dimensions adoptedfor the structure of this invention could result in a well bore beingdrilled with the structure having a radius or detlection of infinity,thus producing a straight bore hole.

Additional purposes and objects of the invention will become apparent asthe description proceeds, which will be given in connection with theaccompanying drawings forming a part thereof and in which:

Figure l is a fragmentary view in side elevation with parts broken away,illustrating a drilling unit suitable for practicing the method andexemplifying the apparatus of the present invention.

Figure 2 is a side elevation of the drilling unit shown in Figure lillustrating the mode of operation of the unit with certain of the partsin an alternate position.

Figure 3 is a detailed sectional view illustrating a structure by whicha deecting force is applied to the drilling unit.

Figures 4a, 4b and 4c 'are cross-sectional views taken, respectively, onlines 4a-4a, 4b-4b, and 4c-4c of Figure l, illustrating the relationshipof the drilling unit axis and the well bore axis in drilling uniformlydeflecting bores having large radii.

Figures 5a, 5b and 5c are cross-sectional views taken, respectively, onlines 5cl-5a, Sb-Sb and 5c--5c of Figure 2, illustrating therelationship of the drilling unitaxis and Well bore axis in drilling,with the drilling unit set-up shown in Figure 2, uniformly deflectingbores of large radii.

Figure 6 is a detailed cross-sectional view taken on line 6-6 of Figure3.

Figure 7 is a fragmentary view in side elevation illustrating a drillingunit exemplifying this invention, producing a bore deflection of uniformlarge radius as a continuation of a well bore having a relatively largedrift angle.

Figure 8 is a detailed sectional View illustrating the manner in whichthe drilling unit may be suspended from a conventional rotary drillstring.

Figure 9 is a detailed sectional view through the clutch mechanismincorporated in the drilling unit and illustrating certain operationalfeatures thereof.

Figure l0 is a fragmentary view in side elevation illustrating a modiedform of drilling unit suitable for practicing the method andexemplifying the apparatus of the present invention.

Figure ll is a fragmentary view in side elevation illustrating anotherembodiment of the drilling unit which may be utilized in practicing themethod and exemplifies the apparatus of the present invention.

Reference will now be had to the embodiment shown in Figure l asillustrating the salient features of the drilling unit of thisinvention. A conventional hollow rotary drill string is indicated at 10which is adapted to extend to the surface of the well and be rotated bythe conventional rotary equipment. Drilling fluid is adapted to bepassed down through the hollow drill string 10 which has suspended atthe lower end thereof a unitary assembly ernbracing an inner tubularrotary drive member 11 which Vcarries the bit 12 at its lower end sothat rotation of the rotary drill string 10 and the rotary tubular drivemember 11 will effect a positive rotation of the bit 12. Snrr'oundingthe rotary drive member 11 is an elongated sleeve 13, the upper end ofwhich is threadably engaged at 14 with a collar 1S carrying antifrictionmeans 16Vto facilitate free rotation of the tubular drive member 11within the sleeve 13. The details of this mounting between the sleeve 13and tubular drive member 11 are more clearly illustrated in Figure 8.

Mounted adjacent the upper end of the sleeve 13 are a pair of collars 17and 18 having parallel longitudinal ribs 19 extending radially thereof.Adjacent the lower end of the sleeve 13 there is provided a pair ofcollars 20 and 21 similar to the collars 17 and 18 and having parallelribs 22 extending longitudinally along the side thereof. limited axialmovement relative to the sleeve 13 while being prevented from rotationrelative to the sleeve 13 by studs 23 mounted in selected ones ofthreaded aper- The collars 17-18 and 20--21 are allowed 4 ture-s 23 inthe sleeve 13. The heads of studs 23 slidably engage with longitudinalslots provided in the respective collars 17, 18, 20 and 21.

Figures 3. and 6 illustrate the details of construction used in mountingthe collars 17 and 18 on the sleeve 13. Particular attention is calledto the plurality of threaded apertures 23 radially spaced around thesleeve 13 as shown on Figure 6. In the specific embodiment illustrated,threaded apertures are disposed radially around the sleeve 13 at 60intervals. The provision of these threaded apertures 23' to receive thestuds 23 enables the orientationv of the respective ribbed collars 17and 18 relative to the sleeve 13 so that such collars may be selectivelysecured at any one of a-plurality of positions of orientation relativeto the sleeve. lt will, of course, be appreciated that the collars 2t)and 21 may be similarly mounted on the sleeve 13 with such mountingbeing capable of being altered as desired to vary the orientation of therespective collars relative to the sleeve 13.

A heavy leaf spring 24 adapted to exert a predetermined lateral force onthe drilling unit has its opposite ends suitably secured to the collars17 and 18, as by welding such ends to the respective collars on the sidethereof opposite the ribs 19. The lower pair of collars 20 and 21likewise has a similar leaf spring 24 secured therebetween as by weldingthe ends of such spring to the collars on the side opposite the parallelribs 22. As shown in Figure 3, the leaf spring 24 in its free positionwould take the form illustrated in dotted lines, causing the collars 17and 13 to move axially toward one another. However, upon insertion inthe well bore, the spring 24 is compressed to the form shown in Figure 3to exert a strong lateral force against the rigid sleeve 13. v

Secured to the lower end of the sleeve 13 as by `suitable threadedconnection, is the upper member 36 of a twof member clutch, the lowermember 31 of which is secured to and carried by the rotary drive member11. A spring 32 normallyrurges the clutch members 30 and 31 axiallyapart toward the disengaged position. When, however, an upward pull isexerted on the drill string 10, the frictional resistance offered by thesprings 24 and the ribs of collars 17, 18, 20 and 21, together with theweight of the parts will tend to retain the sleeve in place so thatlimited vertical movement of the drive member 11 will cause engagementof the clutch members 30 and 31. Upon engagement of the clutch members,rotation of the drive member 11 will cause the sleeve 13 to rotatetherewith to facilitate orientation of the sleeve 13 to effectdeflection of the bit 12 in a desired azimuth.

During the normal drilling operation, the sleeve 13 is disengaged fromthe rotation of the rotary drill string 10 by reason of the spring 32maintaining clutch members 30 and 31 in disengaged position. The sleeve13 is normally held against rotation by engagement of the heavy leafsprings 24 and certain of the ribs 19 and/or 22 carried by the collars,with the well bore, as will be described hereinafter. The engagement ofthe springs 24 and ribs 19 and 22 with the well bore, while preventingundesired rotation of the sleeve 13, will permit such sleeve and theparts carried thereby to move longitudinally with the progress of thedrill bit 12 during the drilling operation. Thus only upon closing ofthe clutch members 30 and 31 upon lifting of the rotary drill string 10followed by forced rotation of the sleeve 13, will the azimuth of thebore deflection be varied. It is further pointed out that the weight ofsleeve 13 and the parts carried thereby is normally of suicientmagnitude so as to overcome the frictional resistance or drag created bysprings 24 and the ribs on collars 17, 18, 2B and 21 engaging with thewell bore. Thus, in normal operation the weight of the sleeve and partscarried thereby will cause it to move along with the drill collar 11 anddrill bit 12.

On the drawings the amount of well bore deviation is exaggerated to moreclearly illustrate the principles of operation of the method of thisinvention and the signifiv cant features of the apparatus of thisinvention. It will be readily recognized that in actual drillingpractice with this invention, the deflection of the bore may vary fromzero, i. e. a straight bore, to a degree of deviation Within theinherent resilient limit of the rotary drill string.

As will become apparent from the description hereinafter, the dimensionsof the parts and their relation to one another on the complete drillingunit at three coutact points or zones determines the degree anddirection of deviation of the well bore in drilling with the apparautsof this invention. Referring specically to Figure l, these zones ofcontact are designated as A occurring at the upper pair of collars 17and 18, B occurring at thel drilling face of the drill bit l2, and Coccurring at the lower pair of collars 20 and 2-1.

Considering further the structural relationship illustrated for thedrilling unit of Figure l, it will be seen that such structure is shownpositioned in a curved bore which bore has been produced by use of theparticular drilling unit. In the structure as illustrated the radiallyprotruding ribs 19 and 22 carrried respectively by the upper and lowercollars are vertically aligned one above the other and the ribs protrudeoutwardly of their respective collars for the same radial distancerelative to the guide sleeve axis at the upper and lower collars, adistance less than the radius of the drill bit 12.

Visualizing the structure ofpldigure l positioned in a previouslydrilled straight bore, the heavy leaf springs 24 exert a force tendingto tilt or laterally displace the sleeve 13 relative to the straightwell bore axis. The drill bit desirably having a radius equal to theradius of the straight well bore would be centered therewithin. Thesleeve 13, acting as a rigid straight guide, is tilted about the drillbit under the lateral displacing force of springs 24a until arrested byengagement of ribs 19 with the straight well bore. With a drilling unitsuch as illustrated by Figure l, the ribs 22 will not engage thestraight well bore, so that the lateral deilecting force of springs 24will 'ce transmitted to the bore wall by ribs i9 and the drill bit 12engaging the well bore adjacent the opposite ends of straight drillguide sleeve 13.

in this condition, rotation of drill bit 12 to extend the length of thewell bore will be attended with a lateral displacing force imparted tothe drill bit by lower spring 2-1, the detlecting force of the upperspring being carried by ribs l? engaging the Well bore wall. Thus asdrilling is continued, employing the drilling unit as shown in Figure l,drill bit 12 will not only proceed downwardly into the formation beingdrilled under the drilling weight applied from the top of the well butalso will progress laterally under the deliecting force of lower spring24 so as to drill a deilected path or bore from the bottom of theoriginal straight well bore.

After a relatively short length of bore hole has been produced employingthe drilling unit of Figure l, the drill bit will have progressedthrough vertical and lateral cornponents Vof movement to a point whereguide sleeve i3, pivoting about tne well bore engaged ribs i9, willcarry ribs 22 into engagement with the Well bore. At this point, ribs 22transmit the lateral deflecting force of lower spring 24 directly to thewell bore wall so that a laterally deecting force is no longertransmitted to the drill bit l2.

Accordingly the drilling unit, in producing a curved well bore, reacheswhat may be termed a stable state wherein continued drilling with theunit Will result in a curved bore of uniform large radius beingproduced. The apparatus in Figure l is shown in such stable state withthe curve of the well bore being produced by use of the drilling unitcorresponding with the circular arc which includes the edge of the drillbit 12, the edges of ribs 22 and the edges of ribs 19 as three zones ofcontact between the bore hole and the drilling unit.

Figures 4a, 4b and 4c illustrate cross sections of the drilling unittaken generally at the three zones of contact and showing the apparatusor Figure 1 in its relation to a curved well bore produced throughutilization of the drilling unit. These figures exemplify therelationship between the axis of such a curved bore produced by thedrilling unit and the straight axis of the drill guide sleeve 13. Thusit will be seen that, with the dimensional characteristics andrleationship of the parts for the drilling unit as shown in Figure 1, aparticular relation between the sleeve axis and curved bore axis will beassumed upon continued drilling with the drilling unit.

it will be appreciated, as exemplilied more fully hereinbelow inconnection with other gures of the drawings, that the drill guide sleeveaxis to well bore axis relationship is determined, when a drilling unitis positioned in a length of curved well bore produced by use of theparticular unit, by the radial distance between the sleeve axis and theouter edges of the well bore engaging ribs on the upper and lowercollars, by the radius of the rotary drill bit and by the orientation ofthe ribs on the upper collars relative to the ribs on the lower collars.Also the longitudinal or axial spacing between the upper collars, thelower collars and the drill bit is a factor entering into thedetermination of the position which the drill guide sleeve axis willassume relative to the axis of the curved bore produced by use of aparticular drilling unit which has predetermined dimensionalcharacteristics and relationship of the parts. These variables determinethe location of the contact Zones A, B and C and relationship of theaxis of the rigid guide sleeve 13 to the contact zones.

ln the description given hereinabove in connection with the operation ofthe drilling unit illustrated in Figure l, it has been noted that thesprings 24 urge the drilling unit toward a particular relation withinthe Well bore as the drilling progresses from say a previously drilledstraight bore to the deviating bore resulting from utilization of thedrilling unit. lt follows that once the drilling unit has arrived atthis hereinabove referred to stable state, continued drilling with theunit will effect production or' a Well bore length continuing in thecurve as determined by the structural characteristics of the particulardrilling unit. Any tendency for the path of the curved well bore tostray from the predetermined curvature determined by the characteristicsof the particular drilling unit will be resisted. For example, if thedrill bit 12 deviates to the right as shown in Fioure l, ribs 22 will becarried by rigid straight sleeve i3 out of engagement with the well boreand the orce of spring 24 will then be transmitted to the drill bitthrough rigid straight sleeve 13 to urge the drill bit as it drills backtoward the desired curve of the well bore to be produced, Likewise ifthe drill bit 12 deviates to the left, sleeve 13, pivoting about ribs22, will lift ribs 1% out of engagement with the well bore wall and theupper spring 24 will transmit a deecting force through sleeve 13 actingas a lever to the drill bit tending to urge it back to the predetermineddesired curve for continued drilling of the well bore.

From the description given hereinabove, it will be apparent that thedistance between the axis of slevee 13 and the outer edges of ribs 19and 22 may be altered as desired to provide a drilling unit which iseffective in use to produce a desired particular inclination of sleeve13 relative to the well bore and hence a predetermined curved deviationof the well bore. Accordingly drilling units may be made up inaccordance with the instant invention to be effective in use forproducing different degrees of inclination and/ or deviation in adifferent azimuth depending upon the radial distance between the sleeveaxis and the outer preiphery of the drilling unit at the three zones ofcontact. ln fact, if the ribs 19 and 22 protrude outwardly to the sameextent so that the radial distance from the sleeve axis to the outeredges of such ribs are equal to one another, and also equal to theradius of the drill bit l2, lthe axis of the sleeve 13 in use of thedrilling unit will be substantially in coincidence with the well boreaxis and thus such drilling unit will *ribbed collar and sleeve`relationship of Figure 1.

. 7 produceV a straight well bore or one havingV a radius of infinity. l

As noted hereinabove the axial spacing between the upper and lowercollars and between the lower collar and the drill bit may be changed toprovide a drilling unit which will have characteristics to produce, inuse, bore detlections of different magnitude and/or azimuth. The eiectof varying the axial spacing of the parts on the drilling unit and itsellect` on the curvature of the bore which will be produced by such adrilling unit will be obvious from inspection of the drawings andspecifically Figures 4a, b and c and 5a, b and c, which demonstrate therelation of the weh bore axis to the axis of the'rigid straight guidesleeve 13.

The collars mounted on the sleeve 13 may also be set thereon to changethe radial direction of force applied by the spring 24 with respect tothe sleeve 13. As illustrative of this possible variation to thedrilling unit, Figure 2 shows a unit similar to that of Figure l, butwith the upper collars 17 and 18 rotated 180 relative to the sleeve 13so that the upper spring 24 acts on the upper end of `the sleeve 13 in adirection opposite to the direction of force applied by the lower.spring 24. Accordingly the sleeve, urged toward a tilted position withinthe well bore by springs 24 in effect guides the direction of drillingdone by the drill bit 12 and reaches a stable position during drillingwhen the ribs 19 engage one side of the well bore and the ribs 22 engagethe opposite side of the well bore. From the view shown in Figure 2, itwill be clear that under this stable condition the sleeve 13 will bemaintained in a definite position relative to the bore as determined bythe radial distance between the axis of sleeve 13 and the outer edges ofupper ribs 19 and the radial distance betweene the axis of sleeve 13 andthe outer edges of lower ribs 22. Continued drilling will result in theguiding sleeve 13 determining the direction of drilling performed by thedrill bit 12 so that the drilling operation will continue in asubstantially uniform curved direction as determined by the tilt presentin the sleeve 13 and radius of the drill bit. As in the arrangement ofFigure l, the springs 24 continuously apply a strong force to urge therespective ribs carried by the collars into engagement with the oppositesides of the well bore. Such ribs prevent rotation of the sleeve 13 butin effect act as guides so that the sleeve 13 moves along with the drillbit 12 as the drilling continues.

Figures a, 5b and 5c show the relationship of the axis of the drillguide sleeve 13 and the axis of the well bore hole, and illustrate howthe relationship of the collars on the sleeve 13 and the direction offorce applied by the springs 24 may be employed to cause a greatercurvature to be lpresent yin the bore as drilled than that with the Thisgreater curvaturev is produced by reason of the upper and lower sets ofcollars engaging opposite sides of the well bore wall so that sleeve-13,upon reaching a stable condition, will have its axis intersect the wellbore axis at a greater angle as clearly shown on Figures 5a, 5b and 5c.

Mention has previously been made as to the possibility of `positioningthe collars 17-18 and 20-21 on the sleeve 13 by utilizing appropriateones of the threaded holes for the studs 23. It will be readilyappreciated that whereas in Figure 2 the two sets of collars have beenshown with the springs 24 acting in opposite direcftions, or in otherwords 180 apart, the collars may be mounted on the sleeve 13 by use ofappropriate threaded holes 23 in the sleeve engaged by studs 23 so thatsuch springs may act in directions other than 180 apart. Obviously thesevariations in positioning of the upper and lower springs 24 will producevarying tilts on the sleeve 13 to eiect well bore deflections ofdifferent radii. In each of the above-described set-ups, a specificsetting of theY springs 24 when used with a rotary drill stringwillproduce a well bore dellection of substantially uniform radius. V v

Figure 7 illustrates an embodiment similar to the drilling unit ofFigures 1 and 2 wherein the ribs 19 and 22 protrude outwardly of theirrespective collars to an extent such that the axis of the sleeve 13 ispositioned for the major portion of its length on the spring side of theaxis of the well bore duringthe drilling operation when the ribs areengaged with the wall of the well bore. The springs 24 continue to applya strong force in urging the ribs 19 and 22 into engagement with thewell bore. The extent of radial protrusion of the ribs 19 and 22as shownin Figure 7 is particularly advantageous in drilling curved bores oflarge radii wherein the drilling is performed at a rather large driftangle. With -ribs 19 and 22 as shown in Figure 7, the weight of theparts is carried by such ribs and as the drift angle increases, theforce applied by springs 24 is assisted by the gravitational pull on theparts to force the ribs 19-22 more strongly into engagement with thewell bore wall. Accordingly, in using this structure at large driftangles the force of springs 24 is not employed to carry thegravitational pull on the drilling unit as would be the situation if astructure such as shown in Figure 1 is used for large drift angledrilling.

Since the relationship of the axis of sleeve 13 and the axis of the wellbore in the structure shown in Figure 7 forms a curved bore in the samemanner as in the structures-of Figures 1 and 2, it is consideredunnecessary to repeat the description of the manner in which the curvedbore of large radius is produced by this apparatus. It will beappreciated that as in the case of the structures of Figures 1 and 2 therelationship of the parts on sleeve 13 in relation to one another and tothe drill bit 12 enter into the determination of the position which theaxis of sleeve 13 assumes relative to the axis of the well bore when theapparatus reaches a stable state for continued drilling of a uniformlycurved well bore. Sufiice it to state that the sole distinction is thegreater distance between the guide sleeve axis and the outer Well boreengaging edges of the ribs 19 and 22 which makes this apparatus moredesirable for use in drilling curved bores where the drift angle isrelatively large, as 40 or greater. As will 4be readily recognized, whenthe apparatus as shown in Figure 1 is initially lowered through astraight bore, with the drill bit being of size substantially equal tothe well bore diameter the upper ribs 19 will engage the well bore walliirst under the urging of springs 24. On the other hand Where the ribs19 and 22 protrude outwardly to an extent as shown in Figure 7 the lowerribs will engage the well bore wall iirst when the apparatus isinitially lowered through a straight bore.

Figure l() illustrates a modified form of the invention adaptable forperforming the method of this invention and disclosing a structuralembodiment of such invention. As in the form of the drilling unit ofFigures 1 and 2, the springs 24 are attached at their opposite ends toaxially spaced collars slidably mounted on the sleeve 13. Thus the upperspring 24 is secured as by welding to the collars 17 and 1S and thelower spring 24 secured to the collars 20' and 21'.

Upper and lower collars 35 and 36, respectively, are' secured to thesleeve 13 as by set screws 37 and are provided with ribs 38 which are toengage the wall of the well bore during drilling of the deecting bore.Upper collar 35 is secured between the opposed ends of the collars 17and 18', with the adjacent ends of said collars being provided withsuitable interengaging elements so that the collars 17 and 18 may moveaxially relative to the xed upper collar 35 but are permitted onlylimited rotational movement relative to such upper collar by suchelements. It will likewise be seen that the lower collar 36 is providedwith interengaging elements at its opposite ends to engage withcooperating elements on the opposed ends of the collars 20 and 21'torestrain relative rotation between such collars.

With this modified structure it will be readily appreciated that thesprings 24 will urge the axis of the sleeve 13 laterally within the Wellbore so that the ribs 38 carried by the collars 35 and 36 will engagethe wall of the well bore. Due to the interengaging elements couplingthe slidably mounted collars to the ends of the xed collars 35 and 36,the springs 24 will be maintained in a position on the opposite side ofthe axis of sleeve 13 from the ribs 33 while being permitted limitedlongituinal movement upon compression of the springs 24.

As in the previous structures illustrated, a line joining the edges ofthe ribs 38 and the edge of the drill bit 12 defines the well bore curvewhich will be continuously formed by utilizing the drilling unit in thewell drilling operation. Thus as in the previously described structures,ribbed collars having ribs protruding to a greater or lesser extent maybe used in place of the collars 35 and 36, to make up a drilling unitwherein the curvature of the bore hole produced by such drilling unitwill be dierent. By employing different ribbed collars the drilling unitmay be varied from a drilling unit capable of producing a straight boreto a drilling unit for producing a bore having a curve within theinherent resiliency of the rotary drill string.

Figure ll discloses an alternative structure adaptable for performingthe method of this invention and disclosing a structural embodiment ofsuch invention. In this structure a single leaf spring 24 is utilized inplace of the pair of springs of the previously described structures,This single spring provides the necessary force to urge the axis ofsleeve 13 laterally relative to the well bore and is secured at itsopposite ends to a pair of collars 41 and 42 which are mounted on thesleeve 13, guided by studs 23. The collars il and 42 are provided withribs 43 which as in the previous embodiments serve to support theguiding sleeve 13 in determining the curvature of the bore created byutilizing the unit on the end of a rotary drill string.

In summary, it may be stated that the effective pressure applied to thebit and the direction of drilling performed by the spring or springs 24in urging the sleeve 13 laterally location of the zones of contact A, Band C along the sleeve 13, the particular radial distance between theguide sleeve axis and the periphery of the drilling unit at each of suchzones, and the direction of the pressure applied by the spring orsprings 24 in urging the sleeve 13 laterally within the well bore.

While the invention is primarily intended to effect drilling of adeflecting bore as a continuation of an initiated straight bore, it ispossible to take off from a well bore that has been previously drilledwith a deecting bore in a predetermined azimuth. Indeed, it is evenpossible to drill a second deflecting bore after a rst bore in a givenazimuth has been drilled. A slight upward pull n the drill string willeffect engagement of the clutch members 30 and 31 so that the unit maybe oriented by partial rotation of the drill string to set up a newazimuth for the deflection of the continued boring of the oil well.

Having thus described my invention, what I claim is:

l. Apparatus for controlling the direction and extent of deviation of awell bore by the rotary drilling method comprising an elongatedrelatively inflexible tubular section, an elongated drill collarrotatably mounted in said tubular section, a drill bit carried at thelower end of and rotatable with said drill collar, means at the upperend of said drill collar for connecting same to the lower end of arotary drill string for rotation therewith, a rst well bore engageablefulcrum forming means mounted adjacent the upper end of said tubularsection and extending outwardly from one side thereof, a lirst well boreengaging dellecting means carried by said tubular section adjacent thepoint of mounting of said rst fulcrum forming means to extend outwardlyfrom the side generally opposite said first fulcrum forming means, asecond well bore engageable fulcrum forming means mounted on saidtubular section at a point spaced below said iirst fulcrum forming meansand extending outwardly from one side thereof, a second well boreengaging deflecting means carried by said tubular section adjacent thepoint of mounting of said second fulcrum forming means to extendoutwardly from the side generally opposite said second fulcrum formingmeans, said well bore engaging deecting means acting to urge therespective fulcrum forming means toward engagement with the wall of thewell bore.

2. Apparatus for controlling the direction and extent of deviation of aWell bore by the rotary drilling method as recited in claim l whereineach of said well bore engaging dellecting means includes a resilientspring carried by the tubular section and engageable with the wall ofthe well bore to impart a lateral deflecting force to the tubularsection for urging the respective fulcrum forming means towardengagement with the opposite side of the well bore.

3. Apparatus for controlling the direction and extent of deviation of awell bore by the rotary drilling method as recited in claim l whereineach of said well bore engageable fulcrum forming means includes collarsmounted on the tubular section and having ribs extending outwardly fromone side thereof and each of said well bore engaging deflecting meansincludes an outwardly bowed leaf spring connected at its opposite endsto such collars and engageable with the well bore wall to impart alateral deectirig force to the tubular section for urging the respectiveribs toward engaffement with the opposite side of the well bore.

4. Apparatus for controlling the direction and extent of deviation of awell bore by the rotary drilling method comprising an elongatedrelatively iniiexible tubular section, an elongated drill collarrotatably mounted in said tubular section and capable of limitedlongitudinal movement relative to said tubular section, interengagingclutch elements carried by said tubular section and said drill collarrespectively, means normally holding said clutch elements in disengagedposition while permitting engagement of said clutch elements uponlimited longitudinal movement of said drill collar within said tubularsection, a drill bit carried at the lower end of and rotatable with saiddrill collar, means at the upper end of said drill collar for connectingsame to the lower end of a rotary drill string for rotation therewithand whereby said drill collar may be moved longitudinally relative tosaid tubular section by lifting of the drill string for engagement osaid clutch elements, a lrst well bore engageable fulcrum forming meansmounted adjacent the upper end of said tubular section and extendingoutwardly from one side thereof, a rst well bore engaging deecting meanscarried by said tubular section adjacent the point of mounting of saidlirst fulcrum forming means to extend outwardly from the side generallyopposite said iirst fulcrum forming means, a second well bore engageablefulcrum forming means mounted on said tubular section at a point spacedbelow said iirst fulcrurn forming means and extending outwardly from oneside thereof, a second well bore engaging dellecting means carried bysaid tubular section adjacent the point of mounting of said secondfulcrum forming means to extend outwardly from the side generallyopposite said second fulcrum forming means, said well bore engagingdeliecting means acting to urge the respective fulcrum forming meanstoward engagement with the wall of the well bore.

5. Apparatus for controlling the direction and extent of deviation of awell bore by the rotary drilling method as recited in claim l whereineach of said weil bore engageable fulcrum forming means includes acollar rigidly mounted on said tubular section and having ribs extendingoutwardly from one side thereof, additional collars slidably engagedwith said tubular section and disposed at the ends of said rigidlymounted collar, an outwardly bowed 1l 12 leaf spring connected at yitsopposite ends to said last men- References Cited in the le of thispatent tioned collars, and means for restraining rotational move- UNITEDSTATES PATENTS ment of said last mentioned collars relative to saidtubular section Y 2,061,316 Brack et al. Nov. 17, 1936 5 2,167,194Anderson July 25, 1939 2,173,309 Monroe Sept. 19, 1939 2,316,409 DowningApr. 13, 1943 2,329,597 Diehl et al Sept. 14, 1943

